ICO stands for Inital Coin Offering, which means someone offers to investors a cryto-tokens or cryptocurrency in exchange of any other cryptocurrency like Bitcoin, Ripple, Ethereum and many more. Since 2013, ICOs used to rased funds of development of new cryptocurrencies. The already created cryptocurrencies sold early, if they have some value or have demand for them.
IEO or Initial Exchange Offering is a concept beyond ICO token sale (Initial Coin Offering). IEO is led by the registered cryptocurrency exchange. In this process, a token sale of a project will be hosted by exchanges such as Bittrex, KuCoin, Huobi, etc, on behalf of the project rather than the project itself. By doing so, the exchange ensures higher security level and prevents price manipulation. IEO is an advanced method of conducting the token sale and raising capital with the help of cryptocurrency exchange.